Piezoelectric devices are used to convert mechanical energy into electrical energy and electrical energy into mechanical energy. Mechanically stressing a piezoelectric device causes a charge imbalance in the device, setting up an electrical field that can be measured. Conversely, applying an electrical field across a piezoelectric device can induce a mechanical stress that can be used to controllably manipulate an object coupled to the device. In some applications, piezoelectric devices can be coupled to the surfaces of objects and used for detecting vibrations in the objects, emitting vibrations into the objects, or both. Examples of this include mechanically coupling piezoelectric devices to flat panels and using the devices to induce vibrations in the panels that lead to audible signals, thus converting the panels into loudspeaker devices. Likewise, panels can be used to receive vibrations that are sensed by piezoelectric devices coupled to the panel, thus converting the panels into microphones. Piezoelectric devices have also been used to detect vibrations induced in a plate by a touch to the plate. The detected vibrations can be used to determine the location of the touch.